Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

345
FXUS63 KLOT 010139
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
839 PM CDT Thu Apr 30 2026

.KEY MESSAGES...

- Generally cool pattern to persist through next week
  with occasional chances for scattered showers.

- Frost development expected away from the Chicago urban core on
  Friday night into early Saturday.

&&

.UPDATE...
Issued at 839 PM CDT Thu Apr 30 2026

Had earlier adjusted PoPs upward for the widespread rain/shower
coverage. A fairly well defined mid-level short-wave over the
region will keep large scale forcing (height falls) going
through the night. This will result in shower activity and
associated cloud cover hanging on deep into the overnight,
especially with eastward extent. Overnight dry air advection
(dew points in the 20s on the western side of the MS River) on
the backside of the short-wave gradually pressing eastward
should finally help erode cloud cover farther west, but not
until towards daybreak. The end result of the above will be a
much more gradual temperature fall through the night, with only
isolated 36-37F readings by daybreak in the northwest 1/3 or so
of the CWA. As dew points will also be dropping at that point,
the potential for frost development is likely quite limited.

Castro

&&

.DISCUSSION...
Issued at 248 PM CDT Thu Apr 30 2026

A broad upper low continues to swirl above the Great Lakes and
adjacent Ontario with several shortwave disturbances noted
pivoting around the low. One of these shortwaves is currently
drifting across eastern IA and stating to move into northern IL
along with its baggy surface low. Associated with these features
is some light rain showers and sprinkles which will continue to
spread across northern IL and eventually into northwest IN
through the rest of the afternoon and evening. While this
initial wave of showers is expected to exit by midnight, another
shortwave (currently in the Dakotas) will pivot into the area
overnight and may bring with it another chance (20-30%) for
showers. Depending on how quickly this second round of showers
exits and clouds scatter out there could be just enough time for
temperatures to cool and lead to some patchy frost development.
The greatest potential for frost at this point is in northwest
IL, but if clouds clear faster that potential could ooze east.
Given the lower confidence on frost coverage have opted to hold
off on a Frost Advisory for now.

Friday will feature similar conditions to today with highs once
again in the mid-50s inland and in the upper 40s near the lake.
Though, cloud cover will be a bit more expansive as yet another
shortwave will be diving through the area. While mostly dry
conditions are expected for most, there is a non-zero chance
(15- 20%) for some isolated showers Friday afternoon. As the
shortwave disturbance exits Friday evening, skies should quickly
clear as a weak surface high moves overhead allowing
temperatures to dip into the lower to mid-30s. The combination
of clearing skies and light winds will make for favorable
conditions for widespread frost development Friday night into
Saturday morning. Should these trends continue we may need a
Frost Advisory for Friday night but will handle that with
tomorrows forecast package if needed. Regardless, anyone with
sensitive plants should take precautions to protect them.

The weak surface high and modest height rises are expected to
persist through Saturday which will give us a dry start to the
weekend. However, the continued northwest winds will keep highs
only in the mid to upper 50s inland and in the upper 40s to
lower 50s near the lake. With the ridging overhead it seems
skies should favor a mostly to partly sunny condition which may
once again lead to some frost development Saturday night into
Sunday especially in northwest IN.

Heading into Sunday, the continued troughing over the Great
Lakes is forecast to deepen as a more amplified shortwave trough
ejects out of Canada into the region. At the same time, another
trough/upper low is forecast to develop and be oozing inland
across southern CA and the southwest. These features will help
to generate stout southwesterly flow across northern IL and
northwest IN on Sunday which will lead to a slight warming trend
with highs in the mid to upper 60s forecast areawide. With the
warmer temperatures will also come the chances for showers and
possibly a few thunderstorms, but latest forecast trends do have
showers/storms holding off until Sunday evening when the
aforementioned Canadian trough arrives. If this trend continues
then Sunday may too be another dry day for us, however, if the
trough speeds up then we could see rain as early as Sunday
afternoon. Outside of the rain potential, winds on Sunday will
be breezy with gusts likely around 30-35 mph.

The better chances for rain from this system is expected to
occur on Monday when the Canadian trough pushes a cold front
through the region. Depending on when the front arrives, there
is a chance that temperatures on Monday could be the warmest of
the week with highs currently forecast to be in the 70s. Though
if the front comes through earlier then highs may be closer to
what we see on Sunday. Regardless, showers and thunderstorms are
expected to develop along the front and move through the area
into Monday night. While forecast soundings do show some decent
deep layer shear (around 35- 40 kts) moisture looks to be a
limiting factor which should keep the threat for any severe
weather low.

The cold front is forecast to shift south of the area on
Tuesday which should return the cooler temperatures to the
region as broad troughing remains over the Great Lakes. Thus,
highs in the 50s (locally cooler near Lake Michigan) should be
expected for the middle and later half of next week.
Additionally, periodic shortwave disturbances will continue to
dive through the broader trough and result in occasional chances
for showers especially towards the later half of next week.

Yack

&&

.AVIATION /00Z TAFS THROUGH 06Z SATURDAY/...
Issued at 705 PM CDT Thu Apr 30 2026

A low to mid-level wave supporting SHRA over the area early
this evening will slowly exit east through late evening.
However, a faster and stronger mid-level wave approaching from
the northwest will allow scattered SHRA to persist well into the
night. For the Chicago terminals, low-end VFR to high-end MVFR
ceilings at TAF issuance will slowly descend into low-end MVFR
levels late this evening and overnight, with a less than 30
percent chance for a period of IFR ceilings in the 08-12Z
window. At RFD, ceilings should remain mostly VFR but may
briefly become MVFR through the night. MVFR ceilings are
expected to scatter and lift after sunrise, with a 5kft (or
higher) cumulus deck developing Friday afternoon. These cumulus
may become sufficiently deep to produce sprinkles or light
showers mid to late afternoon, but kept the TAF dry with chances
remaining under 30 percent.

ENE up to 10 knots at TAF issuance will settle NE around 5
knots late this evening. Winds should then shift NNW and
sporadically gust to near 20 knots Friday morning before a lake
breeze shifts winds NE for the Chicago terminals by early
afternoon. Expect winds to veer SE or become VRB/calm late in
the evening.

Kluber

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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